This invention relates generally to fire-resistant, tile supporting grid systems and the like, and more particularly, to tile supporting members capable of absorbing axial compressive elongation without substantial buckling of the supported ceiling tiles as might occur during abnormal elevated temperatures, thereby preserving the integrity of the ceiling as a fire barrier under such conditions.
The present invention is particularly adapted for use in ceiling tile supporting grid systems of the type comprising a plurality of parallel, spaced main grid members and cross grid members extending transversely between the main grid members and having end portions interlocking therewith. These interconnected grid members generally are suspended from a conventional ceiling or an overhead support structure.
One of the critical problems encountered in these ceiling tile supporting grid structures is to maintain the integrity thereof under abnormally elevated temperatures, such as accompany a fire. Under these high temperature conditions, metallic grid members, which generally are fixed at their end points, expand and buckle whereby the supported ceiling tiles are displaced and sometimes tilted to such an extent that they drop through the openings fromed by the intersecting grid members. As a result, the effectiveness of the suspended ceiling as a fire barrier is destroyed and the overhead ceiling and related support structure is exposed to fire whereby such fire can spread more easily and rapidly through the entire structure.
The prior art has considered structures for accommodating or absorbing thermally induced compression in a supporting grid structure in order to enhance the ceiling integrity during a fire. Such a prior art structure is found in U.S. Pat. No. 3,778,947 issued to Gale E. Sauer and assigned to the assignee of the present invention. As disclosed in the aforesaid Sauer patent, a discrete amount of material is removed or cut-out from the bead portion of the grid member to permit deformation thereof during the thermal compression. However, although the thermal compression can be accommodated, the strength and rigidity of the bead for resistance against normal conditions of handling, installation, and usage are inherently reduced by removal of the cut-out-material. Moreover, such a cut-out approach further results in a bead having a non-continuous profile with potentially rough edges.